In a previous post, I asked what makes a Mac more glamorous than other options. Faruk left an nice comment and mentioned in particular that the Address Book in the Mac OS X was fun. Rather than just aimlessly play around, I just tried the venerable address book in Windows and the one that ships with OS X 10.4.3 and compared the two experiences. I've captured a handful of images that I'll talk briefly about. I'll keep score along the way.
1) Application icon:
OS X
Windows
And for absolute fair comparison, here's a full sized icon:
Winner: OS X.
Comment: Hardly fair in a practical sense as Windows default icons are 32x32 typically. However, I'll still award this one to the OS X address book as it's a nicer icon. The Windows icon, especially at small sizes, is overly detailed and hard to easily identify.
2) Initial experience. What does the user see?
OSX

My name (Aaron) is already in the list as I'm the owner of the machine. It's subtle, but it also labels it as "me." Nice touch.
Windows

Winner: OS X.
Comments: It's not a clear huge winner, but OS X edges out the Windows counterpart for a handful of minor reasons:
- It's a relatively clean user interface. A contact "view" is opened rather than showing a large list of names and e-mail addresses as would be the case in the Windows address book.
- I hadn't chosen to set up an e-mail account yet, so the default label in Windows is "Main Identity's Contacts." Yikes! That's about as bad a label as it could get. In absence of a name, I would have considered "My Contacts" to be a reasonable alternative.
- The Windows address book application shows up for the first time cut off on the side and requiring a horizontal scroll bar (and it has cut off the edge of the search field!)
- Inconsistent wording in Windows: People vs. a contact. Why are different terms used?
- Mac however wastes some space and shows a scroll bar, even though the entry for Apple would have fit nicely without scrolling.
3) Adding a new person.
OS X

On OS X, the "+" button below the "Name" list is clicked to start the process of adding a new entry in the Address Book.
Windows

On Windows, clicking the "New" button, followed by "Contact" adds a new entry.
Winner: Tie
Comments: The OS X entry is interesting, if inconsistent with most other applications. It's pleasent to work with however and easily understood with a small bit of experimentation. The Windows address book, although not interesting, is very consistent with standard Windows applications, meaning most users should have no trouble completing the task of adding a new entry. The downside of the Windows address book is the sheer volume of tabs and entry fields that are available. The OS X address book hides many values, but still presents the most common. To add additional values, such as an e-mail address, the user must click the small green "+" symbol next to the type of value they want to add. Depending on the field, they'll be able to switch the type to something more specific, like "work" e-mail instead of "home."

4) Data validation. Does the application do reasonable data validation on the behalf of the user?
OS X

Windows

Winner: Windows
Comments: OS X, from what I could determine, offered no data validation for my test field, the e-mail address. The Windows address book displayed the error above.
5) Grouping -- can contacts be grouped easily?
OS X

Windows

Winner: OS X
Comments: The OS X grouping feature wins only because it's simpler. It's probably less full featured, but likely most users won't do much grouping anyway. Microsoft address book adds complexity by providing both the notion of folders and groups. Folders are for logical containment only.
Overall winner: OS X
Comments: OS X did win in this round of tests, but not by a huge margin. It offers some minor wins, primarily in the aspect of simplicity. The Windows address book, while functional, suffers primarily from being a bit bloated and somewhat dated. The overall experience prize definitely goes to the OS X address book as it's just more polished. The OS X address book can also store photos (and easily take photos using an attached web cam which is a nice feature). I'm not sure how many people use that feature though -- it's not very practical to have a web cam ready when you're adding a new contact AND have the person in front of your computer. It's fun, but obtaining photos from photo-shy people can be tricky! 